1. Field of the Invention
The present invention relates to a process for producing difluoroiodoacetyl fluoride having high purity in high yield.
2. Description of the Prior Art
Difluoroiodoacetyl fluoride (ICF.sub.2 COF) is useful as the intermediate for various fluorinated compounds or a compound having special characteristics.
For example, difluoroiodoacetyl fluoride can be converted into .omega.-iodoperfluorocarbon vinyl ether which is useful as a source for thermosetting fluorinated resins, by reacting it with hexafluoropropylene oxide and thermally decomposing the product. Difluoroiodoacetyl fluoride can be converted into perfluorosuccinyl fluoride by a deiodocoupling. The resulting perfluorosuccinyl fluoride can be converted into perfluorodicarboxylic acid derivatives which are useful as sources for fluorinated polycondensates such as polyamides and polyesters having excellent heat resistance and chemical stability, by reacting it with a nucleophilic reagent. Difluoroiodoacetyl fluoride can be used as a source for oxalyl fluoride which is useful as an intermediate for various fluorinated compounds.
Heretofore, it has been known to produce difluoroiodoacetyl fluoride by reacting anhydrous lithium chloride with tetrafluoroethylene oxide in acetyl anhydride (U.S. Pat. No. 3,311,658). In this known process, it is indispensable to use tetrafluoroethylene oxide which is not easily produced in view of an explosive reaction and a low yield. Moreover, the yield of difluoroiodoacetyl fluoride is only less than 40% based on tetrafluoroethylene oxide. Therefore, this process is not satisfactory as an industrial process.
On the other hand, the inventors have studied series of reactions of .alpha.,.omega.-diiodopolyfluoroalkane with an oxidizing acid. As a result, it has been found that when .alpha.,.omega.-diiodopolyfluoroalkane having carbon atoms of 6 or more is used fluorinated diacid fluorides are mainly obtained; and when .alpha.,.omega.-diiodopolyfluoroalkane having carbon atoms of 3 to 5 is used, cyclic compounds such as fluorinated lactones and fluorinated cyclic ethers are obtained and when .alpha.,.omega.-diiodoalkane having carbon atoms of 3 to 5 are reacted with fuming sulfuric acid, a ratio of the production of the fluorinated cyclic ether is increased depending upon increase of a concentration of sulfur trioxide, whereas a ratio of the production of fluorinated lactone is increased depending upon decrease of a concentration of sulfur trioxide. (U.S. Pat. No. 4,116,977 and Japanese Unexamined Publication No. 111011/1978).
The present invention has been accomplished by the following novel surprising findings in the series of studies.